PRELIMINARY RESULTS FROM THE PORTABLE IMAGERY QUALITY ASSESSMENT TEST FIELD (PIQuAT) OF UAV IMAGERY FOR IMAGERY RECONNAISSANCE PURPOSES

Abstract

The article presents a set of initial results of a quality assessment study of 2 different types of sensors mounted on an unmanned aerial vehicle, carried out over an especially designed and constructed test field. The PIQuAT (Portable Imagery Quality Assessment Test Field) field had been designed especially for the purposes of determining the quality parameters of UAV sensors, especially in terms of the spatial, spectral and radiometric resolutions and chosen geometric aspects. The sensor used include a multispectral framing camera and a high-resolution RGB sensor. The flights were conducted from a number of altitudes ranging from 10 m to 200 m above the test field. Acquiring data at a number of different altitudes allowed the authors to evaluate the obtained results and check for possible linearity of the calculated quality assessment parameters. The radiometric properties of the sensors were evaluated from images of the grayscale target section of the PIQuAT field. The spectral resolution of the imagery was determined based on a number of test samples with known spectral reflectance curves. These reference spectral reflectance curves were then compared with spectral reflectance coefficients at the wavelengths registered by the miniMCA camera. Before conducting all of these experiments in field conditions, the interior orientation parameters were calculated for the MiniMCA and RGB sensor in laboratory conditions. These parameters include: the actual pixel size on the detector, distortion parameters, calibrated focal length (CFL) and the coordinates of the principal point of autocollimation (miniMCA - for each of the six channels separately.

Evaluating spatial resolution for quality assurance of UAV images

“…As a consequence, the spatial resolutions of the two cameras were 4.5 and 4.9 cm respectively, which turned out to be about the same with theoretical values. In a test field study for portable image quality assessment of UAV images for reconnaissance purpose in 2015, Dabrowski and Jenerowicz [11] manufactured and installed six 70 cm 9 70 cm wood board-sized black sheets, Siemens Star, bar target, and grayscale simultaneously, and tested radiometric, spectral and spatial resolution. Besides, as they mounted Sony Nex-5 RGB camera on a rotary wing UAV, and photographed images at 10 m intervals from a flight height of 10-200 m, these found that GSD changed linearly to flight height.…”

Methodology for Determining Optimal Exposure Parameters of a Hyperspectral Scanning Sensor

“…When imagery is acquired with camera mounted on UAV platform the consideration of the angle α is mandatory. In addition, the GSD values were calculated on the basis of acquired images with a Siemens star (consisting of 96 sectors), that is commonly used as test to determine spatial resolution (Dabrowski et al, 2015;Orych, 2015). Some of acquired images was used for the accuracy control of determined GSD values.…”